The present invention relates to an exhaust air hood for use in air supply and exhaust systems for buildings and the like, and more specifically, to an exhaust air hood capable of reducing backflows into an interior which may be caused by external air flows.
In recent years, dwelling houses have become more and more air tight with a view, for instance, for improving the efficiency of sound insulation and heating. Particularly in cold areas, houses having a gap equivalent area ratio of less than 1 cm.sup.2 /m.sup.2 is about to be realized.
In such highly air-tight houses, interior ventilation is important in order to realize a comfortable living environment, and development of ventilation systems fit for this purpose has been a strong concern.
In these circumstances, conventional ventilation systems fall into two types: mechanical air exhaust systems and mechanical air exhaust-and-supply systems.
In a conventional ventilation system, since the exhaust air port section is located outdoors, the ventilating function of the system is strongly influenced by external winds. Particularly when an exhaust air port happens to be positioned upwind of the system, the ventilating function is lowered, sometimes resulting in the occurrence of a backflow through the exhaust air port, thus failing to effect proper ventilation.
In the case of ventilation through the exhaust air port of a kitchen stove hood or ventilation for a bathroom or water-closet, there exists another problem. When the ventilation system is not in use, external air under wind pressure may flow indoors, causing contaminated air to diffuse into the interior.
The present invention is the result of extensive research conducted in view of the above-described problems. An object of the present invention is to provide an exhaust air hood capable of reducing backflows through exhaust air ports caused by wind pressure, thus enabling a proper ventilation system to be achieved.